Sex-specific joint trajectories of deviant peer affiliation and externalizing problems from middle childhood to early adolescence: the predictive role of family maltreatment.

Previous research has shown a strong link between deviant peer affiliation (DPA) and externalizing problems (EXT) among children and adolescents. Little is known about how DPA and EXT develop jointly over time or possible sex differences in their development. This longitudinal study identified sex-specific joint trajectories of DPA and EXT from middle childhood to early adolescence and investigated the predictive role of family maltreatment experiences in joint trajectories of DPA and EXT. A total of 3622 Chinese elementary school students in grades 3 and 4 (Mage = 10, SD = 0.53; 46.5% girls) comprised the sample. Assessments were conducted every six months on five occasions across 2.5 years. Parallel process latent class growth modeling (PP-LCGM) was used to explore the joint trajectories of DPA and EXT for boys and girls separately. The PP-LCGM identified four trajectories for boys: "congruent-low" (78.2%), "congruent-high" (12.40%), "deviant peer affiliation increasing" (6.5%), and "congruent late increasing" (2.9%). Four trajectories were identified for girls: "congruent-low" (82.5%), "slowly increasing" (10.2%), and "deviant peer affiliation desisting" (5.6%), and "congruent late increasing" (1.7%). After controlling for socioeconomic status (SES), the results showed that compared to the congruent-low group, more severe family maltreatment predicted the high and high-start trajectories for boys. The findings highlighted the joint development of DPA and EXT and the sex differences associated with their development. Findings also shed light on the importance of sex in developmental responses to family maltreatment.